How can I do a monitoring/guard CCTV camera effect with blender?
If you are trying to achieve this effect on the right:



Use the compositor and distort the source image with a Lens Distortion Node in projector mode. This can make it appear like a fisheye lens. Security cameras have a wide field of view. You could add horizontal lines to simulate an old tube monitor screen. Use a wood texture node and scale the x axis to 0 and the y or vertical axis to a very large value, then multiply it with the source, after distortion. 

Also security or guard cameras operate in low light so you could remove the color with a  Hue Saturation Value node.





For extra value you could add glare to the source image to blow out highlites and make a slightly blurry image, as these cameras often have poor optics. If you are making this effect in 3D I would still suggest using the compositor.